SUMMARY: The pH optimum of the ATPase activity in plasma membranes from NCYC 431 from 8 h cultures was around 6·5 and that in membranes from organisms from 16 h cultures near 6·0. The [ATP] of the enzyme was virtually unaffected by the age of the culture from which organisms were harvested, although the of the enzyme in membranes from organisms from 8 h cultures was higher than that for organisms from 16 h cultures. Ethanol noncompetitively inhibited ATPase activity in membranes, although the inhibition constant for the enzyme from organisms from 8 h cultures was lower than that from organisms from 16 h cultures. Glycine accumulation by the general amino acid permease was non-competitively inhibited by ethanol. Inhibition constants were virtually the same for glycine uptake by deenergized organisms from 8 h and 16 h cultures, but under energized conditions the value was greater for organisms from 16 h rather than 8 h cultures. The data indicate that inhibition of plasma-membrane ATPase activity by ethanol could account, at least in part, for inhibition of glycine accumulation by ethanol.


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